Differential calorimetry with sweeping

The differential calorimetry with sweeping (in English, Differential Scanning Calorimetry or DSC) is a method of Caractérisation Matériaux. It measures the differences of the heat transfers between a sample to be analyzed and a reference (for example Alumine, but can also be air).

It makes it possible to determine

the Température of vitreous transition ( T ) from the Polymère S;
temperatures of fusion and crystallization;
the Enthalpy S of reaction (to know the rates of reticulation of polymers).

The analyzes are carried out under sweeping of an inert gas (for example, the Azote or the Argon) to avoid any reaction of material studied with the atmosphere of the furnace.

The apparatus undergoes important changes of temperatures. By consequence, the position of certain elements of the DSC will vary. The whole of calculations realized by the data-processing interface is done compared to the thermocouple positioned between the sample and the reference. While moving, the results will be distorted. It is thus necessary to gauge regularly by checking for example the melting points de using the Indium, of the Zinc or the Plomb (generally, one uses the Indium - T = 156,6 °C; ΔH = 28,45 J·G −1 ).

Difference between differential Calorimetry with sweeping and Analyzes thermal differential

Differential calorimetry with sweeping and the differential thermal Analyze (DTA) are very often confused. There however exists a basic difference between these two methods. With an apparatus of DSC , one measures differences in energies , whereas with the DTA , one measures differences in temperatures . DTA is used very little for the characterization of Polymères because the signals resulting from or the state phase shifts of the matter are of very weak Amplitude.

Method by compensation

This method was invented by the company Perkin Elmer.

The sample and the reference are placed in two different furnaces but in same the calorific Enceinte. The temperature variation between the two furnaces is made simultaneously consequently quantity of Calorie S. the temperature is maintained always equal in the two furnaces, and varies in a linear way.

The differences of the energies absorptive or released by the sample and the reference are measured. When a transition occurs, according to whether it is Endothermique or Exothermique, the sample will absorb or release from energy. A generating of power more or less provides energy compared to the reference. It is this variation of energy which is recorded according to time or of the temperature.

Method of the heat flows

This method was developed by Of the Bridge of Nemours - Mettler.

The sample and the reference are placed in the same furnace. A probe of Platine makes it possible to control and record the change of the temperature of the apparatus. The signal temperature is then converted into calorific signal of power.

This technique measures the differences in heat flow between the sample and the reference during a cycle of temperature. The temperature, provides by a electric resistance , varies linearly.

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